# What is Newtonian: Definition and 336 Discussions

The Newtonian telescope, also called the Newtonian reflector or just the Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design has made it very popular with amateur telescope makers.

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1. ### I Newtonian path of light in a gravitational field

I think this is the appropriate subforum. I'm curious as to what approaches have been taken. I know this prediction isn't correct. I can think of at least a couple ways that I could go about this. They may or may not give the same prediction. One approach would be to simply use kinematics, and...
2. ### MTW Exercise 12.6: Formulating Newtonian Gravity Using Curvature

Hello, I am attempting to work through problem 12.6 in MTW which involves formulating Newtonian Gravity using Curvature as opposed to the standard formulation. This is a precursor before standard GR. In it he states that the curvature tensor in this formulation is as follows...
3. ### B Eddington Exp vs Newton: Comparing Starlight Deflection

The Eddington Experiment famously confirmed GR by showing, as Einstein had predicted, a deflection of starlight by the Sun that was double the deflection expected by Newtonian gravity. I don't understand where Einstein's 2x number came from. I make the following assumptions: 1. That a ray of...
4. ### B Why does ##F## often appear as inverse square laws such as Newtonian gravity?

...y and Coulomb's law diverge as ##r\rightarrow##0? I mean, if a point light source emits light omnidirectionally, the intensity converges at the source, right? THIS is how I should've worded my previous post!
5. ### I Time Travel in Newtonian Spacetime: Is it Possible?

Is time travel possible in Newtonian curved spacetime?
6. ### I Modified Newtonian Dynamics + dark matter sterile neutrinos or PBH?

what about Modified Newtonian Dynamics + dark matter both right and both correct Are sterile neutrinos consistent with clusters, the CMB and MOND? Garry W. Angus arXiv:0805.4014 [ If no sterile neutrinos then Modified Newtonian Dynamics + primordial black holes Primordial Black Holes...
7. ### Question on the Newtonian displacement of light

Hi everyone! Hope your day is going well. I’m an ex-physics student who recently wanted to go back to studying the subject (as a hobby, mostly). So I picked up Zee’s GR book since GR is the thing I’m the most interested in. I expected to hit a wall on some basic things since I’m rusty, and did...
8. ### Motion of a Particle: Solutions & Examples

This is jut an example to illustrate my doubt. I don't know how to obtain the tracjectory given only the acceleration in this format. I realized that if i can show that there is an constat vector 'a' that satisfy a•r=constant, than the motion would be on the surface of a cone. So i tried to make...
9. ### Looking for a book on many body Newtonian dynamics (point masses)

Any book on many body Newtonian dynamics?
10. ### I General relativistic comparison to Newtonian physics

Let's say a small object orbits around massive object at some distance in perfectly circular orbit. In Newtonian physics the force acted upon orbiting body is: Force = m1 * orbital_speed^2 / distance = G * (m1*m2) / r^2 for an object of 1kg orbiting a body of 2*30^kg at the distance of 1.521 *...
11. ### I The bending of starlight is twice the Newtonian prediction

When light is viewed from an accelerating frame of reference it appears to bend at a rate of a/c (the acceleration a being at right angles to c). By the Principle of Equivalence the bending of a beam of light in a uniform gravitational field ought to be g/c rad/sec. In principle you could use...
12. ### Frame indifference and stress tensor in Newtonian fluids

During lecture today, we were given the constitutive equation for the Newtonian fluids, i.e. ##T= - \pi I + 2 \mu D## where ##D=\frac{L + L^T}{2}## is the symmetric part of the velocity gradient ##L##. Dimensionally speaking, this makes sense to me: indeed the units are the one of a pressure...
13. ### A Obtaining the Orbit equation (Effective Potential) from the Newtonian metric

We can write the Newtonian metric in the form of $$ds^2 = -(1 - 2M/r)dt^2 + (1+2M/r)[dr^2 + r^2d\Omega^2]$$ In order to obtain the orbit equation I have written the constant of motion, $$e = (1 - 2M/r)(\frac{dt}{d\tau})$$ and $$l = r^2sin^2(\theta)(\frac{d\phi}{d\tau})$$ I can divide the...
14. ### A Solving Linearized EFE for Newtonian Potential Under Lorentz Gauge

Under the Lorentz Gauge the Einstein Field Equations are given as $$G^{\alpha \beta} = -\frac{1}{2}\square \bar{h}^{\alpha \beta}$$ Then the linearized EFE becomes, $$\square \bar{h}^{\mu\nu} = -16 \pi T^{\mu\nu}$$ For the later parts, I ll share pictures from the book I have couple of...
15. ### Testing Newtonian Gravity: Collision of Two Masses

[Mentor Note: thread split off from a different thread] https://www.physicsforums.com/threads/heavier-objects-fall-faster.1002022/ Since seeing this thread yesterday, I have been trying to derive the time equation for the collision of two masses due to Newtonian gravity. Unfortunately, this...
16. ### I Physics of exercising and forces felt

Let's imagine an ideal scenario where you're lifting your own weight in its entirety. Let's say a woman weighing 100 lbs. Suppose she's doing an idealized handstand and pushup from that position. So she's lifting 100 lbs. Let's say ideally all of the forces are on her arms only. Do these forces...
17. ### Solving for relativistic velocity using Newtonian physics

The answer is tD = [D_0 - 3/4ct - 1/2ct] I just have 2 questions. I realize for 2 vectors approaching it is negative for distance and for velocity positive. What be the rule for time? How do I find vector answers for velocity and distance and time? I am confused why I have "td = ..." ? Can...
18. T

### On the non-applicability of Newtonian mechanics

Hello. The questions are: Why Newtonian mechanics is not applicable to quantum mechanics and more natural phenomena in gravity? So, we needed general relativity which offers a metric theory about gravity and applies to more phenomena in nature, but how is this explained that special and general...
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### I Is it possible to extend Newtonian gravity to include energy as well as mass?

Hello there.My question is:can Newtonian gravity be generalised to include not only bodies with mass but energy also?Thank you.Can my thread be moved to classical physics?
20. ### I Can Newtonian Gravity be Thought of as a Theory of Curved Time?

Before I attempt to delve into the math of tensors and curved spacetime, I'm hoping to get a more general intuitive grasp of things. As such, I'm parsing through a lot of lower level articles on these topics, and several that I've come across have argued that Newtonian gravity can be thought of...
21. ### B Mass of Hanging Rope: Calculate Easily

Hi, I have a question about a hanging rope - how do you find it's mass? I've been searching a long time, stumbled across some advanced calculus involving catenary functions and equations, but couldn't quite figure it out.
22. ### The leaning ladder problem using Newtonian mechanics

$$R - f = m\ddot x$$ $$N - mg = m\ddot y$$ were N and R are the normal reactions from the smooth wall and rough ground. and f is the friction provided by the ground. $$f = \mu N = cot(\phi)N/4$$ i tried to formulate a constraint relation between ##\ddot x## and ##\ddot y## so that I could...
23. ### B Converting Newtonian momentum into relativistic momentum

Hi, I was trying to derive relativistic momentum equation using classical momentum equation but it didn't work. Could you please help me? Thank you! Where am I wrong? Or, is not possible, in any way, to derive relativistic momentum using Newtonian momentum equation? Thanks!
24. ### Derive Newtonian gravity from symmetry?

Is it possible to derive laws of Newtonian gravity from some symmetries?
25. ### I Thought Experiment Proving Newtonian Momentum Not Conserved

On p.170 of French's book on special relativity there is this thougth experiment attributed to Lewis and Tolman (1909). It is about two individuals throwing identical balls of mass M at each other with identical speed. The balls bounce against each other and are caught again. See attached...
26. ### I Newtonian stable universe model

I was discussing a problem related to Einstein's universe model. As we all know its an unstable equilibrium. So a small fluctuation in the density would result in an either expanding or contracting universe. However, I read that "There are static and stable solutions in Newtonian gravity...
27. ### Can analytical mechanics be deduced from Newtonian mechanics?

As you can see from the very last line of my post, this whole post may come from the fact that I don't get sarcasm o0)Hi, reading the above mentioned book I ran into the following footnote: Postulate A was earlier stated as: An alternative, but equal, version of Postulate A is given the page...
28. ### Ridiculously difficult Newtonian physics problem

I have been trying out with this one for a long time with no luck getting the exact expression. I am pretty sure this is somehow related to Kepler's third law but unable to establish the connection and the integrals I get from energy conservation yield different results. Any ideas?
29. ### Conservation laws in Newtonian and Hamiltonian (symplectic) mechanics

In Newtonian mechanics, conservation laws of momentum and angular momentum for an isolated system follow from Newton's laws plus the assumption that all forces are central. This picture tells nothing about symmetries. In contrast, in Hamiltonian mechanics, conservation laws are tightly...
30. ### Introduce Newtonian Metric for SR & Lorentz

Is it meaningful to introduce a Newtonian metric ##ds^2 = dx^2 + dy^2 + dz^2## in analogy with special relavity and the Lorentz metric?
31. ### Do these words have same meaning in Newtonian mechanics?

Are this 2 words have same meaning in Newtonian mechanics: More than 2 non-parallel forces and Coplanar Concurrent Force System?
32. ### Shear and the stress tensor of a Newtonian fluid

Similarly the paper by @buchert and @ehlers https://arxiv.org/abs/astro-ph/9510056 Here the author has defined ##v_{ij}=\frac{\partial v_i}{\partial x_j}=\frac{1}{2}(\frac{\partial v_i}{\partial x_j}+\frac{\partial v_j}{\partial x_i})+\frac{1}{2}((\frac{\partial v_i}{\partial...
33. ### Graphene and Newtonian mechanics

I am writing a paper for "Dynamics and statics" course. I am really interested in Graphene. I am not if this is a good topic for this specific course. Any suggestions? Thank you in advance
34. ### I Newtonian Gravity Vs. Quantum Gravity

I want to know the differences between Newtonian Gravity and Quantum Gravity
35. ### Newtonian Physics: Is it Compatible with Relativity?

Newtonian Physics states in part that 'every object has an absolute state of motion relative to absolute space, so that an object must be either in a state of absolute rest, or moving at some absolute speed.' Granting that if absolute space were to exist, we have no means to measure it at...
36. ### B Newtonian vs. Relativistic momentum

Perhaps naively I assumed that for a relativistic particle the product of mass times velocity would be the same in both Newtonian and Einsteinian mechanics. The simplistic thinking was the mass increase in relativistic dynamics would balance out the non-real superluminal velocity of a particle...
37. ### Does Gravity Deflect Light according to Newtonian Mechanics?

I have read in several popular physics texts that general relativity predicts that gravity deflects light, but that Newtonian mechanics, in contrast, predicts that the trajectory of light is not affected by gravity. However, I am very skeptical and confused about this result. We of course have...
38. ### I Newtonian analogue of energy-momentum relation?

Hi. I've read that there's no Newtonian analogue of the energy-momentum relation $$E^2-(pc)^2=(mc^2)^2\enspace .$$ Why doesn't $$E=\frac{p^2}{2m}$$ qualify as such? There's no rest energy in Newtonian physics anyway.
39. ### I GR vs Newtonian Physics: Mass Curving Spacetime & Gravity Effects

In GR Mass is said to curve spacetime which is the explanation for Gravity versus Newtonian physics where it is explained as all matter attracts each other. My question is how does curved spacetime cause objects traveling at different velocities to follow different paths? If gravity was only due...
40. ### Particle Newtonian Mechanics: Father Pulling 100 lb Sled

Homework Statement The problem states that there is a father pulling a 100 lb sled with a force of 100 lb at some angle. At what angle does the father have to pull in order for the sled to accelerate at 25 ft/s^2? The coefficient of kinetic friction here is given as 0.04. Homework Equations F...
41. ### Is Newton's Equation for Gravity Accurate for All Situations?

I have several questions about the Newtonian equation for Gravity Gm1m2/r^2. First, I want to point out this equation is only valid for point masses or when the two objects are sufficiently far apart.This is because the r squared term on bottom means that the relationship between force and...
42. ### I Is the Schwarzchild Radius Relativistic or Newtonian?

I noticed that the Schwarzschild Radius Formula and the Escape Velocity Formula are actually identical. The Schwarzschild Radius is supposed to be one of the great equations generated from Relativity, while the Escape Velocity is something that was generated just using Newtonian gravity. All you...
43. ### B Can Modified Newtonian Dynamics Explain Dark Matter?

Hello Everbody In Sci Shows newest video they take about alternates to Dark Matter and one of these is Modified Newtonian dynamicse. The guy states that there were two teams one proved that it existed and the other did the the opposite. My question is why they can't and didn't compare there...
44. ### How was Newtonian relativity ruled out in EM propagation?

What I've read on the Michelson/Morley experiment explains that it made the idea of the luminiferous aether seem less likely, but I don't think I've ever seen an explanation of why everyone didn't just assume that light follows normal Newtonian relativity. What I mean is this: according to...
45. ### Velocity is a vector in Newtonian mechanics

I studied the vector analysis in Arfken and Weber's textbook : Mathematical Methods for Physicists 5th edition. In this book they give the definition of vectors in N dimensions as the following: The set of ##N## quantities ##V_{j}## is said to be the components of an N-dimensional vector ##V##...
46. ### Newtonian Mechanics : Rectillinear Motion of a Particle

Homework Statement Find the velocity ± and the position x as functions of the time t for a particle of mass m, which starts from rest at x =0 and t =0, subject to the following force functions: (a) Fx = F0 + Ct (b) Fx = F0 sin Ct Ct (c) Fx = F0e^ct where F0 and c are positive constants...
47. ### Non Newtonian / Newtonian Fluid interface

Suppose I have a wave tank partially filled with a shear thickening Newtonian fluid (Oobleck), on top of which sits a layer of water (separated by a thin membrane to prevent mixing) If I propagate a surface wave in the water layer how will it conduct itself at the Newtonian/Non Newtonian Fluid...
48. ### I Deflection of Starlight by Newtonian Gravity - Example Calculation

So, I have heard that the deflection of starlight using Newtonian gravity is only half of the deflection predicted by Einstein. NE1 know where I can find an example of the former calculation? thanks
49. ### Insights The Schwarzschild Metric: Part 3, A Newtonian Comparison - Comments

Greg Bernhardt submitted a new PF Insights post The Schwarzschild Metric: Part 3, A Newtonian Comparison Continue reading the Original PF Insights Post.
50. F

### Newtonian physics and motion of a wiggling rope

What types of objects does Newtonian mechanics deal with? Is it just rigid bodies? I’m not sure how Newton’s laws could explain something like the motion of a wiggling rope.